A group of investigators within the Howe Laboratory of Ophthalmology of the Massachusetts Eye and Ear Infirmary is applying for funds to replace an obsolete transmission electron microscope under the competitive Biomedical Research Support (BRS) Shared Instrumentation Grant Program. This group of major users are PHS funded investigators whose research programs rely heavily on the use of a state-of-the-art transmission electron microscope. The research grants of the major user group encompass a wide range of research goals in basic studies of vision and ocular disease, including studies of the etiology, pathobiology and treatment of ocular melanomas and retinoblastomas (Albert); transmission electron micrographic studies of aminoglycoside-induced outer retinal injury (D'Amico); morphologic studies of the trabecular meshwork in glaucoma (Epstein); transmission electron micrographic studies of the mucous layers of the preocular tear film in normal and diseased human conjunctiva (Foster); transmission electron microscopic studies of laser-induced vascular injury in the choroid, and retinal injury following ultrashort (e.g. femtosecond) laser pulses (Puliafito); and ultrastructural studies of the trabecular meshwork, including studies of extracellular matrix components, cytoskeletal elements, and phagocytosis (Richardson). The current electron microscope in the Howe Laboratory is out-of- date and inadequate to achieve the research goals outlined in these PHS funded projects. Instruments located in other laboratories are unavailable to realize the research plans of these investigators. We have developed a cooperative organizational plan with an internal advisory committee to coordinate the operation and maintenance of the transmission electron microscope and have secured institutional support for installation of the instrument, service, and support personnel to promote maximum utilization of the instrument.